Basic Research On The Erosion Of Converter Lining For Production Of Low-carbon And Phosphorus Steel

Aiming at the serious erosion of the lining of 150 t converter for low-carbon and phosphorus steel production,the erosion mechanism of converter lining,production process,slag and maintenance technology were studied by thermodynamic simulation,laboratory and industrial experiments.Through above research,the erosion mechanism of converter lining in the production of low carbon and phosphorus steel was clarified,the endpoint control and auxiliary material adding process in the late stage of converter smelting were optimized,proposed comprehensive maintenance technology.This paper provides theoretical and technical supports to improve the lining life and keep stable production.Based on the study on the erosion mechanism of converter lining,it is concluded that the RO phase and phosphorus-rich phase in the dense slag layer have a protective effect.The melting temperatures of RO phase and phosphorus-rich phase are 1878℃ and 1973℃,and they account for 58～73%and 17～26%,respectively.Increasing the temperature or the oxidation of the slag can increase the saturation solubility of MgO,leading to the erosion of the dense slag layer.Continuous invasion of slag and peeling off the decarburization layer,that a new dense slag layer was formed.The cycle that the decarburization,peeling off of the decarburized layer and saturation and dissolution of the dense slag layer repeats and gradually loses its internal barrier effect.The study on the effect of the converter production process on lining erosion shows that the endpoint carbon content should be greater than the critical carbon content of selective oxidation of carbon and iron at the end of the blowing.Shorten the press lance time to 40～70 s,which can control the endpoint C content greater than the critical C content and reduce the FeO content of the final slag.When the temperature and the C content at the end of blowing were 1650±10℃ and 0.03wt%,corresponds to the control range of the FeO%was 29.7～31.8wt%.It is proposed the pouring temperature and FeO content in slag can be effectively reduced by controlling the endpoint carbon content at 0.040～0.050wt%,and then decarburize by 24.2%on average through static stirring.When the press lance position,the top blowing flow and the bottom blowing flow were controlled as 1.3～1.4 m,32000 Nm3/h and 300 Nm3/h,it can ensure that the liquid level fluctuation was in a low range,reduce droplet splashing and impact area.After process optimization the FeO content in the slag was reduced by an average of 7.48wt%,the erosion of lining was significantly reduced.Through the study of slag erosion converter lining,it can be seen that the large number of basic phases are unfavorable to reduce the erosion of the converter lining,while the RO phase will promote the formation of dense slag layer.The mass transfer of the original grain iron in the slag was oxidized,the Fe content in the RO phase,basic phase and phosphorus-rich phase added from 37.36wt%to 70.38wt%,29.94wt%to 34.45wt%,1.43wt%to 2.41 wt%,respectively.The proportions of phosphorus-rich phase,basic phase and RO phase in the early slag are 68.82%,17.20%and 13.98%,respectively.The proportion of phosphorus-rich phase,basic phase and RO phase in the final slag decreases to 45.35%,30.23%and 24.42%,respectively.Thus,the erosion effect of the final slag on the converter lining is obvious.In addition,reducing the FeO content and increasing the MgO content of the slag at the converter end-blowing stage can reduce the erosion of the slag.The research on the maintenance technology and serious erosion area of converter lining show that the trunnion part of the converter lining was prone to form a serious erosion area,and the maximum erosion rate of this part was 61.1%.The best splash slag composition is FeO:20～24wt%,MgO:8～9wt%,R:3.5～4.0.Through the water model experiment,it was determined that when the splash slag lance position,the top blowing flow and the slag amount were 2.1 m,32000 Nm3/h and 100 kg/t,respectively,the amount of slag at the trunnion was the largest,the area of serious erosion was reduced.Based on the application of comprehensive lining maintenance technologies,the total erosion area of the converter lining is reduced by 1.24 m2.